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| United States Patent |
5,344,593
|
|
Chiba
, et al.
|
September 6, 1994
|
Electroconductive elastomer-forming composition
Abstract
An electroconductive elastomer-forming composition comprising (a) 100 parts
by weight of a vinyl group-containing polydimethylsiloxane having a
standard polystyrene-reduced molecular weight of 10,000-40,000, (b) 5-50
parts by weight of a hydrosilyl group-containing polydimethylsiloxane
having a standard polystyrene-reduced molecular weight of 10,000-40,000
and (c) 30-1,000 parts by weight of electroconductive particles. Said
composition can form a conductor of small thickness having good
conductivity, excellent heat resistance and excellent durability.
| Inventors:
|
Chiba; Hideki (Hitachi, JP);
Igarashi; Hisao (Fukushima, JP);
Yasuda; Naoshi (Komatsu, JP);
Matsuki; Yasuo (Oita, JP)
|
| Assignee:
|
Japan Synthetic Rubber Co., Ltd. (Tokyo, JP)
|
| Appl. No.:
|
853813 |
| Filed:
|
March 19, 1992 |
Foreign Application Priority Data
| Current U.S. Class: |
252/514; 252/512; 252/513; 524/862; 528/15; 528/31; 528/32 |
| Intern'l Class: |
H01B 001/00; H01B 001/20; H01B 001/22 |
| Field of Search: |
252/502,503,511,512,513,514,518
524/862
528/15,31,32
|
References Cited
U.S. Patent Documents
| 4547312 | Oct., 1985 | Graiver et al. | 252/513.
|
| 4552688 | Nov., 1985 | Sakamoto et al. | 252/511.
|
| 5075038 | Dec., 1991 | Cole et al. | 252/514.
|
| Foreign Patent Documents |
| 0173560 | May., 1986 | EP.
| |
| 0264635 | Apr., 1988 | EP.
| |
| 0273003 | Jun., 1988 | EP.
| |
| 0300380 | Jan., 1989 | EP.
| |
| 0367562 | May., 1990 | EP.
| |
| 2605326 | Apr., 1988 | FR.
| |
| 56-91302 | Jul., 1981 | JP.
| |
| 57-53602 | Nov., 1982 | JP.
| |
Primary Examiner: Lieberman; Paul
Assistant Examiner: Kopec; M.
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt
Claims
What is claimed is:
1. An electroconductive elastomer-forming composition consisting of (a) 100
parts by weight of a vinyl group-containing polydimethylsiloxane having a
standard polystyrene-reduced molecular weight of 10,000-40,000, and up to
5% by weight based on component (a) of another polysiloxane, (b) 5-50
parts by weight of a hydrosilyl group-containing polydimethylsiloxane
having a standard polystyrene-reduced molecular weight of 10,000-40,000,
and up to 5% by weight based on component (b) of another hydrosilyl
group-containing polysiloxane, (c) 30-1,000 parts by weight of
electroconductive particles, an inorganic filler other than the
electroconductive particles and a curing catalyst.
2. The composition according to claim 1, wherein the polydimethylsiloxane
(a) contains vinyl groups at the two terminals.
3. The composition according to claim 1, wherein the molecular weight
distribution index (standard polystyrene-reduced weight-average molecular
weight, Mw/standard polystyrene-reduced number-average molecular weight,
Mn) of the component (a) is 2.0 or less.
4. The composition according to claim 1, wherein said another polysiloxane
is a vinyl group-containing polydimethylsiloxane whose molecular weight is
different from that of the component (a), or a vinyl group-containing
polydimethylsiloxane whose molecular weight is different from that of the
component (a) and whose methyl groups are partially substituted with
phenyl groups.
5. The composition according to claim 1, wherein the component (b) has a
hydrosilyl equivalent in a range of 350-1,100.
6. The composition according to claim 1, wherein the Mw/Mn of the component
(b) is 2.0 or less.
7. The composition according to claim 1, wherein said another hydrosilyl
group containing polysiloxane is a hydrosilyl group-containing
polydimethylsiloxane whose molecular weight or hydrosiyl equivalent or
both of them are different from those of the component (b), or a
hydrosilyl group-containing polydimethylsiloxane whose molecular weight is
different from that of the component (b) and whose methyl groups of
siloxane are partially substituted with phenyl groups.
8. The composition according to claim 7, wherein the proportion of the
component (b) to the component (a) is 10-30 parts by weight per 100 parts
by weight of the component (a).
9. The composition according to claim 1, wherein the electroconductive
particles (c) are particles of at least one metal having
electroconductivity.
10. The composition according to claim 9, wherein the metal having
electroconductivity is nickel, iron, copper, zinc, chromium, silver,
cobalt or aluminum.
11. The composition according to claim 9, wherein the metal having
electroconductivity is nickel, iron or copper.
12. The composition according to claim 1, wherein the electroconductive
particles (c) are nickel particles whose surfaces are coated with gold.
13. The composition according to claim 1, wherein the electroconductive
particles (c) have particle diameters of 3-200 .mu.m.
14. The composition according to claim 1, wherein the proportion of the
electroconductive particles (c) is 10-750 parts by weight per 100 parts by
weight of the component (a).
15. The composition of claim 1, wherein the inorganic filler is aerogel
silica.
16. The composition of claim 1, wherein the curing catalyst is a platinum
catalyst obtained by adding
tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane to sodium
chloroplatinate.
Description
The present invention relates to an electroconductive elastomer-forming
composition. More particularly, the present invention relates to a
composition which can form an electroconductive elastomer having good heat
resistance and good durability.
Currently, conductors are in wide use as a conductor for inspection of
circuit substrates, electronic parts, etc. or as a switch element of
electronic apparatus, etc.
As such conductors, there have heretofore been widely used conductors
comprising a high-molecular elastomer and conductive particles dispersed
therein.
In recent years, in the field of integrated circuits, as electronic parts
have come to be used therein in a higher density, integrated circuits of
flat package type with multipins (e.g. QFP type) have come to become a
main stream in place of integrated circuits of DIP type in which terminals
are inserted into a substrate. When an integrated circuit of flat package
type is inspected for performance, an inspection method employing a
conductor as mentioned above is advantageously used because in the
conventional inspection method in which electrical contact between circuit
substrate and external leads is achieved by contacting the circuit
substrate with metal terminals, the intervals between leads are narrow, so
that the structure of an inspection socket is complicated.
Conventional conductors, however, have low heat resistance and, when they
are exposed to high temperatures for a long time, the elastomer contained
therein undergoes deterioration and its electroconductivity is reduced, or
the elastomer seizes on a circuit substrate to be inspected. Hence, the
use of a conventional conductor in reliability tests at high temperatures
(e.g. burn-in test) poses a problem, and seizure on TAB carrier, in
particular, is a big problem.
When such an inspection of an integrated circuit for surface mounting is
carried out using a conductor, it is preferable in a practical inspection
to form a layer of an electroconductive elastomer-forming composition in a
paste form in a desired thickness on the surface of the lead electrode
area of the circuit substrate on the inspection socket side and then cure
the layer to form a conductor which can ensure electrical contact between
circuit substrate and external leads.
Heretofore, however, there has been known no electroconductive
elastomer-forming composition which can be suitably used to form a
conductor by a step as mentioned above and which can give a conductor
usable stably for a long time even in high-temperature tests such as
burn-in test.
The present inventors have made research for solving the above problems
and, as a result, found an electroconductive elastomer-forming composition
capable of forming a conductor of small thickness having good
conductivity, excellent heat resistance and excellent durability.
According to the present invention, there is provided an electroconductive
elastomer-forming composition comprising 100 parts by weight of a vinyl
group-containing polydimethylsiloxane having a standard
polystyrene-reduced molecular weight of 10,000-40,000 (referred to
hereinafter as "component (a)"), 5-50 parts by weight of a hydrosilyl
group-containing polydimethylsiloxane having a standard
polystyrene-reduced molecular weight of 10,000-40,000 (referred to
hereinafter as "component (b)") and 30-1,000 parts by weight of
electroconductive particles (referred to hereinafter as "component (c)").
Component (a)
The polydimethylsiloxane containing vinyl groups preferably at the two
terminals (component (a)) is the main component of the composition of the
present invention, which forms the main portion of an elastomer upon
curing. The component (a) can be obtained generally by subjecting
dimethyldichlorosilane or a dimethyldialkoxysilane to hydrolysis reaction
and condensation reaction in the presence of dimethylvinylchlorosilane or
a dimethylvinylalkoxysilane and subsequently subjecting the reaction
product to repeated dissolution-precipitation for fractionation.
The component (a) having vinyl groups at the two terminals can also be
obtained by subjecting a cyclic siloxane such as
octamethylcyclotetrasiloxane to anionic polymerization in the presence of
a catalyst and stopping the polymerization using an end terminator to
obtain a polymer (as the end terminator, there is selected, for example,
dimethyldivinylsiloxane; the reaction conditions (e.g. the amount of
cyclic siloxane and the amount of end terminator) are selected
appropriately). In this case, as the catalyst, there can be used, for
example, an alkali such as tetramethylammonium hydroxide,
n-butylphosphonium hydroxide or the like and a solution of a silanolate of
said alkali; and the reaction temperature is, for example,
80.degree.-130.degree. C.
The commercial products of the component (a) include, for example, KE-77 (a
product of Shin-Etsu Chemical Co., Ltd.), TSE-201 (a product of TOSHIBA
SILICONE CO., LTD.), SILASTIC 410 and 430 (products of TORAY INDUSTRIES,
INC.) and SILAPLANE FP-2224 and FM-2231 (products of CHISSO CORPORATION).
When the molecular weight of the component (a) is less than 10,000, the
resulting electroconductive elastomer has a high hardness and is brittle,
making it impossible to obtain a good elastic state. When the molecular
weight of the component (a) is more than 40,000, a good elastic state can
be obtained but the resulting conductor has low heat resistance and, when
used at high temperatures of, for example, about 150.degree. C., may seize
on, for example, a circuit substrate with which the conductor is in
contact. The molecular weight of the component (a) is preferably
15,000-35,000.
The molecular weight distribution index (the ratio of standard
polystyrene-reduced weight-average molecular weight and standard
polystyrene-reduced number-average molecular weight (referred to
hereinafter as Mw/Mn)) of the component (a) is preferably 2.0 or less in
view of the heat resistance of the electroconductive elastomer to be
obtained.
To the component (a) may be added other polymer in such an extent that the
effect of the present invention is not impaired. Said other polymer
includes vinyl group-containing polydimethylsiloxanes whose molecular
weights are different from that of the component (a); vinyl
group-containing polydimethylsiloxanes whose molecular weights are
different from that of the component (a) and whose methyl groups are
partially substituted with phenyl groups, i.e. vinyl group-containing,
phenyl group-modified polysiloxanes such as vinyl group-containing
dimethylsiloxane-diphenylsiloxane copolymer, vinyl group-containing
dimethylsiloxanemethylphenylsiloxane copolymer, vinyl group-containing
polymethylphenylsiloxane, vinyl group-containing
methyltetrachlorophenylsiloxane-dimethylsiloxane copolymer and the like;
vinyl group-containing, alkyl group-modified polysiloxanes such as vinyl
group-containing polymethylethylsiloxane and the like; and vinyl
group-containing, fluorine-modified polysiloxanes such as vinyl
group-containing polymethyl-3,3,3-trifluoropropylsiloxane and the like.
The content of said other polymer is preferably 5% by weight or less based
on the component (a), in view of the heat resistance of the resulting
electroconductive elastomer.
Component (b)
In the present invention, the hydrosilyl group-containing
polydimethylsiloxane (component (b)) is a component acting as a curing
agent for the component (a) which is the main component. The component (b)
can be obtained generally by subjecting dimethyldichlorosilane or a
dimethyldialkoxysilane to hydrolysis reaction and condensation reaction in
the presence of a hydrosilane compound such as dimethylhydrochlorosilane,
methyldihydrochlorosilane or a dimethylhydroalkoxysilane and subsequently
subjecting the reaction product to repeated dissolution-precipitation for
fractionation.
The component (b) can also be obtained by subjecting a cyclic siloxane to
anionic polymerization in the presence of a catalyst and stopping the
polymerization using an end terminator to obtain a polymer (as the end
terminator, there is selected dimethylhydrochlorosilane,
methyldihydrochlorosilane or a dimethylhydroalkoxysilane; the reaction
conditions (e.g. the amount of cyclic siloxane and the amount of end
terminator) are selected appropriately). In this case, as the catalyst,
there can be used, for example, an alkali such as tetramethylammonium
hydroxide, n-butylphosphonium hydroxide or the like and a solution of a
silanolate of said alkali; and the reaction temperature is, for example,
80.degree.-130.degree. C.
The commercial products of the component (b) include, for example,
SILAPLANE FH-121 and PS-123 (products of CHISSO CORPORATION).
When the molecular weight of the component (b) is less than 10,000, the
resulting electroconductive elastomer has a high hardness and is brittle,
making it impossible to obtain a good elastic state. When the molecular
weight of the component (b) is more than 40,000, the resulting conductor
has low heat resistance and, when used at high temperatures of, for
example, about 150.degree. C., may seize on, for example, a circuit
substrate with which the conductor is in contact. The molecular weight of
the component (b) is preferably 15,000-35,000.
The hydrosilyl equivalent of the component (b) is preferably in the range
of 350-1,100. When the hydrosilyl equivalent is more than 1,100, the
resulting cured elastomer tends to have surface tackiness and reducing
workability.
The Mw/Mn of the component (b) is preferably 2.0 or less in view of the
heat resistance of the electroconductive elastomer to be obtained.
To the component (b) may be added other polymer in such an extent that the
effect of the present invention is not impaired. Said other polymer
includes hydrosilyl group-containing polydimethylsiloxanes whose molecular
weights and/or hydrosilyl equivalents are different from those of the
component (b); hydrosilyl group-containing polydimethylsiloxanes whose
molecular weights are different from that of the component (b) and whose
methyl groups of siloxane are partially substituted with phenyl groups,
i.e. hydrosilyl group-containing, phenyl group-modified polysiloxanes such
as hydrosilyl group-containing dimethylsiloxane-diphenylsiloxane
copolymer, hydrosilyl group-containing
dimethylsiloxanemethylphenylsiloxane copolymer, hydrosilyl
group-containing polymethylphenylsiloxane, hydrosilyl group-containing
methyltetrachlorophenylsiloxanedimethylsiloxane copolymer and the like;
hydrosilyl group-containing, alkyl group-modified polysiloxanes such as
hydrosilyl group-containing polymethylethylsiloxane and the like; and
hydrosilyl group-containing, fluorine-modified polysiloxanes such as
hydrosilyl group-containing polymethyl-3,3,3-tirfluoropropylsiloxane and
the like. The content of the polymer is preferably 5% by weight or less
based on the component (b), in view of the heat resistance of the
resulting electroconductive elastomer.
In the present invention, the proportion of the component (b) to the
component (a) is 5-50 parts by weight, preferably 10-30 parts by weight
per 100 parts by weight of the component (a). When the proportion of the
component (b) is less than 5 parts by weight, the curing state of the
resulting electroconductive elastomer is insufficient, making it
impossible to obtain a good elastic state. When the proportion is more
than 50 parts by weight, the cured electroconductive elastomer has a high
hardness, making it impossible to obtain a good electroconductive
elastomer, and the elastomer yellows and undergoes thermal deterioration
when used at high temperatures.
In the component (a) (vinyl group-containing polydimethylsiloxane) and the
component (b) (hydrosilyl group-containing polydimethylsiloxane), a part
(for example, 2-15%) of the methyl groups in the molecule are preferably
substituted with phenyl groups. In that case, the resulting
electroconductive elastomer has particularly high heat resistance.
The above-mentioned standard polystyrene-reduced molecular weight is a
value obtained by subjecting a sample (0.5 g of a polymer dissolved in 100
ml of tetrahydrofuran) to gel permeation chromatography using a
constant-temperature high-speed gel permeation chromatogram HLC-802 A (a
product of TOYO SODA MFG. CO., LTD.) having a column TSK-GEL (3/8 inch-30
cm, a product of TOYO SODA MFG. CO., LTD.) at a flow rate of 1 ml/min. The
standard polystyrene used was a product of Pressure Chemical Co. of USA.
Component (c)
As the electroconductive particles (c), there can be used known particles
of metals having electro-conductivity, such as nickel, iron, copper, zinc,
chromium, silver, cobalt, aluminum and the like, and particles of alloys
of at least two of said metals having electroconductivity.
Of these, particles of such metals having electroconductivity as nickel,
iron and copper are preferable in view of the economy and
electroconductivity. Nickel particles whose surfaces are coated with gold
are particularly preferable.
Electroconductive carbon black may also be used.
The particle diameters of the component (c) are preferably 3-200 .mu.m,
particularly preferably 10-100 .mu.m. When electroconductive particles
having such particle diameters are used, it is possible to obtain, in the
resulting electroconductive elastomer during its use, sufficient
electrical contact between the electroconductive particles.
The shape of the electroconductive particles are not critical but are
preferably spherical or star-shaped in view of the dispersibility in the
component (a) and the component (b) or their mixture.
The nickel particles whose surfaces are coated with gold, used particularly
preferably as the component (c) are obtained by coating gold on the
surfaces of nickel particles by electroless plating. The nickel particles
whose surfaces are coated with gold, have very low contact resistance. The
film thickness of gold plating is preferably 1,000 .ANG. or more.
In the present invention, the component (c) is used in a proportion of
30-1,000 parts by weight, preferably 50-750 parts by weight, per 100 parts
by weight of the component (a). When the proportion of the component (c)
is less than 30 parts by weight, the resulting electroconductive elastomer
shows no sufficiently low electrical resistance when it is used, and
therefore has no sufficient connecting function. When the proportion is
more than 1,000 parts by weight, the resulting cured elastomer is brittle,
making difficult its use as an electroconductive elastomer.
The electroconductive elastomer-forming composition of the present
invention comprising the components (a), (b) and (c) may comprise, as
necessary, an inorganic filler such as ordinary silica powder, colloidal
silica, aerogel silica, alumina or the like. The inclusion of such an
inorganic filler allows the uncured composition to have sufficient
thixotropy, a higher viscosity and improved dispersion stability of
electroconductive particles and the cured elastomer to have an improved
strength.
The amount of the inorganic filler used is not critical. However, its use
in too large an amount is undesirable because the sufficient orientation
of the electroconductive metal particles in a magnetic field is
impossible. Incidentally, the viscosity of the electroconductive
elastomer-forming composition of the present invention is preferably in
the range of 100,000-1,000,000 cp at 25.degree. C.
In the electroconductive elastomer-forming composition of the present
invention, the component (b) acts as a curing agent for the component (a)
which is the main component of the composition, whereby curing takes
place; in particular, when the composition is heated, crosslinking
reaction takes place, whereby an elastomer of high elasticity is formed;
and the elastomer has a function as an electroconductive elastomer because
it contains the component (c).
The electroconductive elastomer-forming composition of the present
invention may comprise a curing catalyst to cure the composition. Said
curing catalyst may be any curing catalyst as long as it is usable as a
catalyst for hydrosilylation reaction, and specifically includes known
curing catalysts such as chloroplatinic acid and its salts,
platinum-unsaturated group-containing siloxane complexes, complex between
vinylsiloxane and platinum, complex between platinum and
1,3-divinyltetramethyldisiloxane, complexes between triorganophosphine or
phosphite and platinum, platinum acetylacetonate chelate, complexes
between cyclic dienes and platinum, and the like.
The method of addition of the curing catalyst is not critical. However, the
curing catalyst is preferably mixed with the component (a) (the main
component) in advance, in view of the storage stability of the
composition, the prevention of uneven distribution of the curing catalyst
during components-mixing, etc.
The amount of the curing catalyst used is preferably determined
appropriately in view of actual curing rate, working life, etc. In order
to control the curing rate and the working life, it is possible to use, in
combination with the curing catalyst, a hydrosilylation
reaction-controlling agent conventionally used such as amino
group-containing siloxane, hydroxyl group-containing siloxane or the like.
The electroconductive elastomer-forming composition of the present
invention is in a paste form. The composition is formed into an
appropriate film and then cured while or after applying, as necessary, a
parallel magnetic field to the composition in the thickness direction to
orientate the electroconductive metal particles contained in the
composition, whereby an electroconductive elastomer in a sheet form can be
formed.
In applying a parallel magnetic field, a magnetic plate having areas of
different magnetic intensities can be used to form an anisotropic
electroconductive sheet in which the distribution of the component (c) is
uneven and electroconductive portions and insulating portions exist. The
electroconductive portions of the sheet may show pressure-sensitive
electroconductivity under which said portions give reduced resistance when
pressed in the thickness direction.
The electroconductive elastomer-forming composition of the present
invention is coated on the surfaces of any desired portion of a device,
requiring electrical connection, for example, the surfaces of the lead
electrode portion of a circuit substrate and then cured while or after
applying, as necessary, a parallel magnetic field to the coated
composition in the thickness direction, whereby an electroconductive layer
can be formed in a state in which said layer is bonded or adhered to said
portion in one piece.
The electroconductive elastomer-forming composition of the present
invention may comprise a silane coupling agent and/or a titanium coupling
agent, whereby the conductor after curing can have sufficient adhesion to,
for example, a circuit substrate.
Thus, the electroconductive elastomer-forming composition of the present
invention is very useful as a material for forming, for example, (1) a
burn-in board for burn-in test of integrated circuits, integrated circuits
for surface mounting having a large number of leads, in particular, (2) an
electroconductive elastomer used as a connector for inspection of various
electronic parts and circuit substrates particularly at high temperatures,
and (3) an electroconductive elastomer used as a switch element of
electronic apparatus requiring heat resistance.
In the electroconductive elastomer-forming composition of the present
invention, each of the vinyl group-containing polydimethylsiloxane (which
is the main component for forming an electroconductive elastomer) and the
hydrosilyl group-containing polydimethylsiloxane (a curing agent) has a
molecular weight of a specific range and the electroconductive particles
are contained in a specific proportion. Hence, the composition, when
cured, can give an electroconductive elastomer which shows excellent heat
resistance and good high-temperature durability, which has no fear of
seizure on a circuit substrate, etc. with which the elastomer is
contacted, and which has good electroconductivity.
The present invention is hereinafter described in more detail referring to
Examples. However, the present invention is by no means restricted by the
Examples. In the Examples, parts refer to parts by weight.
The component (a), the component (b), the component (c), the inorganic
filler and the curing catalyst used in the following Examples are as
follows.
Component (a)
a1: SILAPLANE FP-2224 (polydimethylsiloxane having a weight-average
molecular weight of 18,000 and vinyl groups at the two terminals (a
product of CHISSO CORPORATION))
a2: SILAPLANE FP-2231 (polydimethylsiloxane having a weight-average
molecular weight of 34,000 and vinyl groups at the two terminals (a
product of CHISSO CORPORATION))
a3: SILAPLANE PS-444 (polydimethylsiloxane having a weight-average
molecular weight of 42,000 and vinyl groups at the two terminals (a
product of CHISSO CORPORATION))
a4: SILAPLANE FM-2241 (polydimethylsiloxane having a weight-average
molecular weight of 76,000 and vinyl groups at the two terminals (a
product of CHISSO CORPORATION))
a5: SILAPLANE FM-2242 (polydimethylsiloxane having a weight-average
molecular weight of 99,000 and vinyl groups at the two terminals (a
product of CHISSO CORPORATION))
Component (b)
b1: SILAPLANE FM-1121 (hydrosilyl group-containing polydimethylsiloxane
having a weight-average molecular weight of 11,500 (a product of CHISSO
CORPORATION))
b2: SILAPLANE PS-123 (hydroxilyl group-containing polydimethylsiloxane
having a weight-average molecular weight of 19,000 (a product of CHISSO
CORPORATION))
Component (c)
Metal particles 1: Nickel particles having an average particle diameter of
40 .mu.m
Metal particles 2: Obtained by applying electroless plating to 100 parts of
nickel particles (average particle diameter: 40 .mu.m) using 2 parts of
gold (this amount of gold is an amount which gives a gold film thickness
of 1,200 .ANG. when the nickel particles are assumed to be truly
spherical).
Inorganic Filler
Aerogel silica: AEROSIL R821 (trade name) (a product of NIPPON AEROSIL CO.,
LTD.)
Curing Catalyst
A platinum catalyst consisting of a light yellow, transparent liquid
obtained by adding tetramethyl-1,3-5,7-tetravinylcyclotetrasiloxane to a
mixture consisting of 10 parts of sodium chloroplatinate, 10 parts of
ethanol and 3 parts of sodium bicarbonate, heating the resulting mixture
at 70.degree.-75.degree. C. for 1 hour, removing volatile components from
the mixture under the conditions of 95.degree. C. and 25 mmHg (absolute
pressure) while blowing nitrogen gas, to obtain a mixture of a yellow
liquid and a solid, cooling the mixture and filtering the resulting
mixture.
EXAMPLES 1-4 AND COMPARATIVE EXAMPLES 1-4
A mixture of component (a), component (b), component (c), inorganic filler
and curing catalyst according to the compounding recipe shown in Table 1
or 2 was kneaded using a twin-roll, for 20 minutes. The kneaded product
was thoroughly deaerated under vacuum to obtain compositions in a paste
form.
Each of the compositions was placed in a plate-like mold having a groove of
1.2 mm in depth. The composition in the mold was extended into a sheet
form with a roll or a squeegee, and the sheet was cured in a hot booth at
150.degree. C. for 30 minutes to obtain electroconductive elastomer sheets
of 1.2 mm in thickness.
Heat Resistance Test
Each of the above-obtained electroconductive elastomer sheets was put on a
gold-plated circuit substrate or TAB carrier tape; the resulting assembly
was allowed to stand at 150.degree. C. while applying a load of 2
kg/cm.sup.2 ; and the occurrence of seizure was examined with the lapse of
time.
The results are shown in Tables 3 and 4. In Tables 3 and 4, heat resistance
was evaluated based on the following yardstick.
A: There occurred neither bleeding nor sticking to substrate caused by
seizure.
B: There occurred bleeding which was barely observed visually, or sticking
to substrate caused by seizure to such an extent that the elastomer sheet
did not slip down.
C: There occurred bleeding which was clearly observed visually, or sticking
to substrate caused by seizure to such an extent that the elastomer sheet
was peeled by hand.
D: There occurred bleeding on the whole surface, or sticking to substrate
caused by seizure to such an extent that the elastomer sheet was not
peeled by hand.
Preparation of Circuit Substrate Device Having Anisotropic
Electroconductive Elastomer Sheet Layer
Each of the above-obtained compositions was printed on the lead electrode
portion of a circuit substrate having 240 lead electrodes each made of
copper of 0.15 mm in width (electrode-to-electrode pitch: 0.25 mm), in a
width of 1.0 mm and in a layer thickness of about 0.3 mm in a direction
orthogonal to the direction of the backside of electrodes; the printed
composition was cured at 150.degree. C. for 30 minutes while applying a
parallel magnetic field in the thickness direction, to form an anisotropic
electroconductive elastomer sheet layer in a state in which the sheet
layer and the circuit substrate formed one piece; thus, circuit substrate
devices each having an anisotropic electroconductive elastomer sheet layer
was produced.
Durability Test
To the anisotropic electroconductive sheet layer portion of each of the
above-obtained circuit substrate devices was applied a load of a weight
which yielded a strain of 25% to the sheet layer; each circuit substrate
device was allowed to stand at 150.degree. C. under said load; with the
lapse of time, the resistance of the anisotropic electroconductive
elastomer sheet layer in the thickness direction was measured on each lead
electrode and average of the electrical resistance values of 240 lead
electrodes was calculated. The results are shown in Tables 3 and 4.
TABLE 1
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Example
1 2 3 4
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Component (a)
Kind a1 a1 a1 a2
Weight-average molecular
18,000 18,000 18,000
34,000
weight
Molecular weight distri-
2.0 2.0 2.0 1.7
bution index
Purity (% by weight)
96 96 96 96
Amount used (parts)
100 100 100 100
Component (b)
Kind b1 b1 b2 b1
Weight-average molecular
11,500 11,500 19,000
11,500
weight
Molecular weight distri-
1.6 1.6 1.6 1.6
bution index
Purity (% by weight)
96 96 95 96
Hydrosilyl equivalent
1,000 1,100 350 1,100
Amount used (parts)
30 30 15 15
Component (c)
Metal particles 1 (parts)
158 -- ` 143 143
Metal particles 2 (parts)
-- 158 -- --
Inorganic filler (parts)
18 18 18
18
Curing catalyst (ppm)
10 10 10 10
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TABLE 2
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Comparative Example
1 2 3 4
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Component (a)
Kind a3 a3 a4 a5
Weight-average molecular
42,000 42,000 76,000
99,000
weight
Molecular weight distri-
1.9 1.9 1.6 1.6
bution index
Purity (% by weight)
97 97 94 88
Amount used (parts)
100 100 100 100
Coponent (b)
Kind b1 b1 b1 b1
Weight-average molecular
11,500 11,500 11,500
11,500
weight
Molecular weight distri-
1.6 1.6 1.6 1.6
bution index
Purity (% by weight)
96 96 96 96
Hydrosilyl equivalents
1,100 1,100 1,100
1,100
Amount used (parts)
15 15 15 9
Component (c)
Metal particles 1 (parts)
143 -- 143 137
Metal particles 2 (parts)
-- 143 -- --
Inorganic filler (parts)
18 18 18
18
Curing catalyst (ppm)
10 10 10 10
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TABLE 3
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Time Example
Temp. (hr) Substrate 1 2 3 4
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Heat resistance
140.degree. C.
100 TAB carrier tape
A A A A
Circuit substrate
A A A A
250 TAB carrier tape
A A A A
Circuit substrate
A A A A
500 TAB carrier tape
B A A B
Circuit substrate
B A A B
Durability (.OMEGA.)
Room Initial -- 0.29 0.20 0.25 0.31
temp.
150.degree. C.
100 -- 0.31 0.22 0.27 0.33
200 -- 0.36 0.29 0.31 0.38
300 -- 0.38 0.27 0.34 0.39
400 -- 0.39 0.30 0.37 0.42
500 -- 0.40 0.31 0.38 0.42
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TABLE 4
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Time Comparative Example
Temp. (hr) Substrate 1 2 3 4
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Heat resistance
140.degree. C.
100 TAB carrier tape
C C C C
Circuit substrate
C C C C
250 TAB carrier tape
C C C D
Circuit substrate
C C C D
500 TAB carrier tape
D D D D
Circuit substrate
D D D D
Durability (.OMEGA.)
Room Initial -- 0.32 0.25 0.35 0.37
temp.
150.degree. C.
100 -- 0.34 0.30 0.40 0.41
200 -- 0.37 0.32 0.45 0.45
300 -- 0.40 0.34 0.49 0.49
400 -- 0.45 0.39 0.53 0.53
500 -- 0.52 0.45 0.57 0.60
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